Packers are frequently used in oil and gas production to isolate one portion of a wellbore from another. After being set in a wellbore for what could be as long as many years, these packers need to be retrieved. Several designs have been incorporated in the past for retrievable packers. One such packer, known as a seal-bore-type, packer was run in on wireline. After setting the packer on wireline, tubing was run and connected to the packer by means of an anchor. In order to retrieve this type of packer, the production tubing had to be disconnected from the packer and removed from the wellbore. A separate trip into the wellbore was then required with a specially designed retrieving tool that released the mechanisms within the packer to allow it to be unset and retrieved. Since the additional run of tubing was made with heavyweight drillpipe with or without jars, which allowed for tensile loads higher than the standard production tubing, these types of packers were often used and easily retrieved. Often these packers, after remaining in the wellbore for many years, required the additional tensile loads that could be applied through the heavy-wall tubing in combination with jars. These high-tensile loads were necessary due to parts corroding together or debris settling out around the packer. While this type of design allowed for retrieval, it was only at the expense of running the heavy-wall tubing into the hole on a separate run. Typical of such packers are packers made by Baker Oil Tools under Product No. 646, also called RETRIEVA-D; RETRIEVA-DB; and RETRIEVA-DAB LOCK-SET retrievable packers.
Another type of packer previously used is referred to as a modified tubing-set packer. This particular type of packer could be set on a wireline. Part of the assembly of the packer included a seal nipple and an on/off tool. These components were connected to the packer mandrel above the packer and were left in the well when the packer was set. The production tubing was then run in and engaged with the on/off tool seal nipple. The packer was retrieved by manipulating the tubing in combination with rotation and tension to release the packer. The packer was then retrieved on the production tubing. While this technique was desirable because it did not require an additional tubing run, as indicated with the previously described seal-bore-type packers, such packers have been found to be less reliable when it comes to retrieval than the seal-bore packers, primarily due to the tensile limits of the production tubing string, the on/off tool, and the packer mandrel. Typical of such assemblies of the modified tubing-set packer are a wireline-set Uni-Packer VI made by Guiberson.AVA, a division of Dresser Industries. Nipples which convert permanent or retrievable packers into temporary bridge plugs and which are carried in with the packer when it is set are known in the art and one such product is made by Baker Oil Tools, Model RS, Product No. 66548 Setting Nipple.
Accordingly, an objective of the present invention is to provide a packer or bridge plug which can be tubing-released but if such mode of release for any reason does not function to release the packer or bridge plug, a back-up method of release with a releasing tool is also available for the same packer. The alternative method of release functions akin to the operation of the seal-bore-type packers and requires the additional run into the wellbore with heavy-wall tubing to be used. Accordingly, the objective of the invention is to give a greater confidence level to operators beyond that previously experienced with using only a modified tubing-set packer. Now, with the present invention, if the modified tubing-set packer with the production tubing string fails to release, an alternative release mechanism is available.